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Path: utzoo!linus!philabs!prls!amdimage!amdcad!cae780!weitek!mahar
From: mahar@weitek.UUCP (mahar)
Newsgroups: net.arch
Subject: Re: Re: RISC (really on multiplication d
Message-ID: <233@weitek.UUCP>
Date: Thu, 18-Jul-85 13:25:19 EDT
Article-I.D.: weitek.233
Posted: Thu Jul 18 13:25:19 1985
Date-Received: Sat, 20-Jul-85 14:49:47 EDT
References: <149@mips.UUCP> <600005@pbear.UUCP> <493@mmintl.UUCP>
Organization: Weitek Corp. Sunnyvale Ca.
Lines: 12
Summary: Try the PDP-10

In article <493@mmintl.UUCP>, franka@mmintl.UUCP (Frank Adams) writes:
> Which is that integer multiplies are hardly ever (never, in my
> experience) defined in a manner suitable for their most common use.
> I would guess, conservatively, that well over 90% of the integer multiplies
> that are done generate a result with no more bits than the larger of the
> two operands.  That is, one multiplies two words and wants a word result.
> But hardware multiplies invariably generate a two word result, leaving the
> high-order word to be allowed for and/or disposed of.

The Decsystem-10 & 20 has an instruction IMUL which does exactly what you
want. It Multiplies a 36bit value by another 36 bit value and gives a 36
bit result. They also have a divide which divides a 36 bit number.